JPH0214188B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method and apparatus for manufacturing thermoplastic bags.

Machines for producing bags from thermoplastic web material come in a variety of configurations, depending on the size and type of bag to be produced, and are accommodating the thickness of the material and its chemical composition. Some types of bag-making machines are equipped to produce a certain type of bag, such as a bag with welded sides or a welded bottom; can be accomplished by replacing certain elements.

The purpose of advances in thermoplastic bag manufacturing machinery is to reduce, either directly or indirectly, the time required to manufacture bags. The most important point for reducing the bag manufacturing cycle is whether the bag manufacturing machinery is provided so that the bags are accumulated in continuous and orderly piles, and each pile is loaded with a predetermined number of bags. The point is that it is virtually completely dependent on that. A method currently being attempted for calculating the number of bags and obtaining a consistent bag pile is the use of a conveyor known as a wicket, which accumulates the bags in a pile. Such an accumulation conveyor basically includes a plurality of sets of wicket pins that are successively placed at a deposition station and remain there until a predetermined number of bags have been deposited on the pins at the same station. . According to this method, each bag is provided with a pair of holes that correspond to the wicket pin spacing. Once the predetermined quantity of bags has been accumulated, the advance of the web is stopped and the conveyor carrying the pin sets transports the completed bag stack away from the stacking station, and then the conveyor carrying the pin sets transports the completed bag stack away from the stacking station, and then the conveyor carrying the pin sets transports the completed bag stack away from the stacking station, and then the conveyor carrying the pin sets transports the completed bag stack away from the stacking station. is placed on the deposition station.

The problems of wind friction have little effect on the successful deposition of bags, and hundreds of low-gauge, high-density polyethylene bags can be deposited quickly and accurately, making it easy to use wicket pins. Machines using type deposition equipment are in very widespread use.

In accordance with the present invention, a flat tubular web formed of a thermoplastic web is advanced intermittently along a passageway in uniform increments toward a sealed cutting station;
A method of manufacturing thermoplastic bags in which the web is hermetically cut to form web pieces of a desired size at a hermetic cutting station, the step of advancing the web a predetermined length into the area of a punching device prior to hermetically cutting the web. forming at least one pair of holes at symmetrically spaced locations on either side of its longitudinal centerline in the web advanced a predetermined length; sealing and cutting the perforated length of the web; 1 on both sides of the center line by making a sealed cut at
forming a web piece with a predetermined lateral width so as to obtain pairs of symmetrical bags; placing the pins on a deposition device located in a deposition station with the same number of pins as the number of holes drilled in the web; depositing the web pieces by passing the web pieces through the holes of the web; when the predetermined number of web pieces are placed on the deposition apparatus through the pins of the deposition apparatus to obtain a web piece stack;
advancing the stacking device into the area of the cutting device; and cutting the web piece stack midway between the pins along the centerline with the cutting device; A method of making a thermoplastic bag is provided that includes the steps of forming a stack of.

Further according to the invention, an apparatus for producing thermoplastic bags includes a sealed cutting station for forming a continuous web piece so that two bags are obtained from a flattened tubular thermoplastic web piece; downstream of the sealed cutting station; a rotary transfer device mounted on the side; and a conveyor having pins, the rotary transfer device being adapted to deposit the web pieces from the sealed cutting station in a stack onto the pins of a deposition device suspended from the conveyor. , the bag manufacturing apparatus is further provided with a cutting device, which cuts each stack of web pieces at a point where the stack of web pieces is conveyed downstream from the deposition point by a conveyor. A thermoplastic bag manufacturing apparatus is provided which is adapted to form two bags from a piece of web.

Further in accordance with the invention, an apparatus for manufacturing thermoplastic bags from a roll of flat, tubular web material formed from a thermoplastic web, comprising: a web advancement device for advancing the web intermittently in equal increments; stopping the web; At least one cut on each side of the longitudinal centerline of the web before sealing the web during
a punching device for punching holes; a sealing cutting device extending transversely with respect to the advance path of the web and provided on the sealing cutting station for sealing and cutting the leading portion of the web to obtain web pieces WS; and Once the pieces have been formed, each web piece has a rotary transfer device that transports each web piece onto one of the deposition devices in the deposition station SS, which uses pins equal to the number of holes drilled in the web piece to separate each web piece. has a pin through which the
Further, the deposition device is intermittently brought to the deposition station by an indexable conveyor so that during conveyor stops the web pieces are stacked as a stack on the deposition device through the pins, the conveyor being positioned at the deposition station. Once a predetermined quantity of web pieces has been deposited on one of the stackers, it is again advanced to bring the following stacker to the stacking station, and the bag making machine is further moved downstream of the conveyor path from the stacker station. two at a time by cutting the stack of laterally spaced web pieces along its longitudinal centerline.
An apparatus for manufacturing thermoplastic bags is provided having a cutting device for obtaining a stack of bags.

Further in accordance with the present invention, in an apparatus for manufacturing thermoplastic bags, a web advancement device for intermittently advancing a flat, tubular web of thermoplastic material; a punching device for punching one hole on each side; a sealed cutting device installed in a sealed cutting station for cutting the web transversely with respect to the direction of web advancement and sealing the web to form a perforated web piece; A depositing apparatus having pins extending from a plate and having a spacing corresponding to the spacing between the holes on each side of the center line of the web pieces, so that the central portion of each web piece is on the platform. a rotary transfer device for placing each web piece in a stack along an arcuate path on a deposition device in which each web piece is threaded through a pin so that the web piece is positioned; once a predetermined number of web pieces have been deposited on the platform; a conveyor for transporting the deposition device to a location downstream from the deposition station; and a cutting device located downstream from the deposition station for cutting the stack of web pieces along a centerline. An apparatus for producing thermoplastic bags is provided in which two groups of bags are obtained from a pile of web pieces held by pins on a deposition device by cutting or welding.

The bag manufacturing speed achieved by the method and apparatus of the present invention is twice the operating cycle time of conventional machines of this type, and the physical properties of the material, such as its lack of rigidity, make it difficult to accurately produce bag pieces. In depositing and transporting the deposited body to subsequent processing equipment,
It is no longer a limiting factor. According to the method and apparatus of the present invention, even when processing the thinnest and lowest density polyethylene, it is possible to obtain bags that are multiples of the number of web pieces at one time by cutting a stack containing several hundred web pieces. Can be done.

Prior to the present invention, conventional bag making machines deposited web pieces by passing them through a wicket pin on one side of the bag making machine's stacking device so that the web pieces hung from the wicket pin. According to this method, only a single bag stack can therefore be obtained. According to other bag making machines, the web piece is placed flat on a conveyor, the web piece is punched, and then the web piece is cut into two bags, which are then punched to form two bags. The web pieces were passed through the wicket pin using punched holes and deposited. Therefore, two groups of bag piles could not be obtained from one web piece pile at the same time.

On the other hand, according to the present invention, the web pieces are successively passed through the wicket pin of the stacking device of the bag making machine, so that the web pieces are deposited symmetrically with respect to the wicket pin, and then the web piece pile is cut in two. In this way, two groups of bag piles can be obtained simultaneously. The production speed of the bags is therefore doubled.

The entire bag manufacturing process of the method of the present invention and the apparatus used to carry it out will be described below with reference to the accompanying drawings.

With combined reference to FIGS. 1A and 1B,
Thermoplastic bag making equipment is generally designated by the designation number 20. The main components of the bag manufacturing apparatus 20 are a payout stand 22 that rotatably supports a roll made of thermoplastic material (hereinafter also referred to as a web roll WR) on a shaft 24;
and a plurality of idler rolls 2 that guide the thermoplastic web TF to a tension control mechanism 28 mounted on the frame 30.
Contains 6. The web consists of multiple stationary play rolls 3
2 and a plurality of idler rolls 34 mounted for rotation within a vertically movable crosshead 36. The crosshead 36 is a tubular rod 38 through which a rope or cable 40 is passed.
guided vertically by The end of the cable 40 is coupled to a weight 42 and the cable 40 is attached to a pulley 44.
It progresses in a generally rectangular loop.
Since the sum of the weights of roll 34 and crosshead 36 is greater than weight 42, this difference in weight causes the crosshead to descend, thereby lowering idler roll 3.
Tension is applied to the thermoplastic web stretched between 2 and idler roll 34. The thermoplastic web then passes through idler rolls 46 , 48 , 50 and is further directed towards perforation device 52 . Perforation device 52 has a perforation wheel 54 and a web drive roll 56;
One drive roll 56 functions as a platen roll for the perforation wheel 54. Two rows of perforating pins are arranged on the circumferential surface of the perforating wheel 54, and when the perforating wheel rotates, pins for perforating are arranged in two rows at the same positions across the longitudinal centerline of the web passing between the perforating wheel and the web drive roll 56. 2 parallel to the center line
The book is perforated. This perforation makes it easier to separate the completed bag from the web stack along the perforations after the web stack has been cut along its longitudinal centerline and removed from the deposition apparatus. This is useful if the centerline CP of the web stack has been welded.
The web then passes through a dancer device 58 which applies and maintains a predetermined amount of tension on the web portion downstream of the drive roll 56. play roll 46
A gusset forming device 60 is mounted between the idler roll 48 and the idler roll 48 and between the idler roll 48 and the idler roll 50, and the gusset forming device 60 is configured to bend both side edges of the thermoplastic web inwardly. Operate.

The web discharged from the dancer device 58 passes over idler rolls 62 and between web advancement devices, ie, tension rolls 64 . tension roll 6
4 is located adjacent to a sealed cutting station 66, ie, a web piece forming device, comprising a sealing roll 68 and a vertically reciprocating sealing rod 70. The sealing bar 70 is heated by a heating device (not shown) to perform a seal cutting operation on the web to form uniformly sized web pieces. play roll 62
and the bag forming machine 7 between the sealed cutting station 66 and the sealed cutting station 66.
Four accessory sections 72 are provided, in which a punching device 76 is arranged. As will be described in more detail below, the punching device 76 operates with a pair of pneumatic actuators 125 when the web is stopped to form, for example, a four hole pattern in the central area of the web. Note that while sealing and cutting the web as described above,
The web is gripped on each side of the hole between the hole and the opposite edges of the web by suitable gripping devices (not shown).

The web portion emerging from the sealed cutting station 66 is supported by a series of belts 78 which travel on a generally triangular track in profile, defined by idler pulleys 80 and drive pulleys 82. The series of belts 78 are laterally spaced from each other. As soon as the web piece advancing from the sealing rod 70 is cut and sealed by the sealing rod, it is retained by the radially extending arm 84 of the rotary transfer device 86. The structure and operation of this rotary transfer device 86 are known. Arm 84 has a series of apertures connected to a vacuum source that contact the web pieces to provide a web gripping action. The web piece is then rotated substantially 180 degrees from the belt 78 and placed on the deposition device 88. Deposition device 88
elongated members spaced apart from each other and extending upwardly in a pattern substantially matching the pattern of holes formed by punching device 76;
That is, the pin 90 is supported. As can be seen with reference to FIG. 1B, such a deposition device 8
8 are mounted on a conveyor 92, and the conveyor 92 is driven by an indexing drive device 94, and has an idler sprocket 96 and a drive sprocket 9.
8 along the path given by . Along the upper run of the conveyor 92 and on the frame 100 there is a cutting device or a cutting and joining device 10 according to the invention.
2 is installed. This device is provided for cutting a stack of web pieces to form two groups of bag stacks.

Once the predetermined quantity of web pieces has been deposited on the deposition device located at deposition station SS, the advancement of the thermoplastic web located upstream of the sealed cutting station 66 is temporarily stopped until the subsequent deposition device 88 reaches the deposition station SS. will be stopped. Deposition device 8
During the formation of a stack of web pieces on 8, the web pieces on the downstream deposition device located directly below the cutting device 102 are lowered by two actuators 106 operating simultaneously. The knife 104 cuts along the center line CP in the advancing direction of the deposition device, and thus two groups of bag deposits are instantaneously obtained.

The method of depositing web pieces from a thermoplastic web and subsequently dividing the web stack so that two bag stacks are obtained from each web piece is common practice and according to the present invention. , after aligning and depositing hundreds of web pieces as a complete stack, a cutting device at a cutting station CS;
Alternatively, it becomes possible to effectively cut the web piece indexed towards the cutting and joining device. The advantages of processing the web using the apparatus exemplified above are:
It is possible to process the thinnest, lowest density polyethylene film.

FIG. 2 shows the web pieces captured by the arm 84 of the rotary transfer device 86 being deposited onto a deposition device 88 located at a deposition station SS.

3 and 4 show a cutting device according to the present invention,
That is, the structure of the cutting and joining device 102 is shown, and the fifth
Figures 7 to 7 show its operating mode. As can be seen from the drawings, the frame 100 has a plate 138 on which the pressure actuator 106 is mounted, and an actuation rod 140 projects through an aperture in the plate 138. In order to resist the bending moment applied to the plate 138, a hollow beam 142 having a square cross section is firmly fixed to the plate 138 by welding or the like. A carrier plate 146 is fixed to the lower end of the actuating rod 140 by a threaded stator 144, and a holder 152 is fixed to the carrier plate 146 via a stator 148 and a spacer 150. Holder 152
includes a clamp bar 154 and a clamp bar 15
4 is a knife 10 having a sharp serrated blade portion 158;
Holds 4. Push plates 160 are disposed on both sides of the holder 152 in close proximity to the holder, each push plate 160 being rigidly coupled to a guide rod 162 that is biased downwardly by a spring 164. Each guide rod has a bush 16 fixed to a plate 146.
6 and is retained within the bushing by a threaded nut 168. Referring to FIG. 4, the pressing plate includes the knife 10.
4 cuts the stack of web pieces to form individual bag stacks, while the stack of web pieces is cut to form individual bag stacks, the stack of web pieces is pressed downward, and the individual bag stacks are pressed by a pressing plate. It can be seen that the device 88 is also restrained on the deposition device 88 by pins 90a and 90b.

To facilitate the cutting or joining operation of the web stack, the holder 152 is heated and heat is transferred to the knife 104 carried by the holder. Heat is supplied to an elongated cylindrical resistance heater 170 associated with an electrical temperature controller (not shown);
The temperature of knife 104 is adjusted. When cutting the cut edge (cut surface) of a web piece without bonding or fusing it, it becomes very easy to cut when the temperature of the knife is between 93°C and 105°C. It has been found that this high temperature can reduce the knife thrust force required to cut the pile of web pieces. If you want to cut the web pieces and simultaneously fuse and bond the cut edges, increase the temperature of the knife to about 298°C. Although the various temperatures described above may provide desirable results for certain types of thermoplastic webs, the skilled person can select the level of temperature that best suits the particular requirements of the web to be used. .

A suitable conventional controller is provided to control the flow of air pressure to the actuator 106, thereby extending and retracting the actuating rod 140 to accomplish the cutting of the web piece.

In order to sharpen the blade 158 of the knife 104 as the knife 104 penetrates the pile of web pieces, the deposition device 88 is provided with a flat rectangular plate 172 on which a block of wood 174 is fixed. . The use of the wood block 174 provides a very rigid and flexible reaction surface that allows the knife to cut through entire web sections and increases the life of the blade of the knife 104. It became clear.

The operation of successively passing web pieces through pins generally indicated by the reference number 90 on the deposition device 88 to form a stack of web pieces is performed by a pair of pins 90a.
This can be reliably achieved by making it shorter than the pair of pins 90b (see FIG. 2). The height difference between each set of pins 90a, 90b is such that the plane containing the upper ends of the pins is substantially coplanar with the plane containing transfer arm 84. Therefore, when the web piece is threaded through pin 90, pins 90a, 90
b pass through hole 130 substantially simultaneously.

5, 6, and 7 illustrate the operation of a cutting device, or cutting and joining (sealing) device 102, which includes a knife 1 as previously described.
It operates depending on the temperature of 04. When the deposition device 88 reaches directly below the device 102, the web piece carried by the pin 90 has a centerline CP indicating that it is a cut surface.
divided along. If the temperature of the knife 104 is approximately 105° C., the web pieces will be cut (FIG. 6), but this cut portion of the web will be joined (welded).
Not done. Thus, when the web piece is split, two sets of bag stacks BS are produced, which are held by pins 90 on the stacking device.

If it is desired to join or close the separated web pieces at their cut surfaces, the temperature of the knife should be about 298°C, so that the edges 176 of the bag stack are cut when the knife passes through the stack of web pieces. Welded (see Figure 7). As the stacker carrying the two groups of bag stacks advances past the cutting device 102, the stacks can be unloaded by an operator. However, the upper stroke of conveyor 92 is such that it does not proceed at such a speed that the pile must be removed quickly.

[Brief explanation of drawings]

FIGS. 1A and 1B are a side elevational view of the thermoplastic bag manufacturing apparatus when connected; FIG. 2 is a perspective view showing the placement of web pieces in the deposition apparatus located at the deposition station Figure, 3rd
The figure is an enlarged side view of a cutting device for dividing web pieces or a cutting and joining device, and FIG. 4 is an enlarged side view of the cutting device of FIG. 3.
or an enlarged end view of the cutting and joining device; FIG. 5 is a perspective view of the deposition device located at the cutting station; and FIG. 6 is a perspective view showing the web piece being cut and supported by the pins of the deposition device , Figure 7 is the 6th
FIG. 3 is an end view of the figure. 88... Deposition device, 102... Cutting device (cutting and joining device), 104... Knife, 140... Operating rod, 160... Pressing plate, SS... Deposition station, CS... Cutting station, CP... Web Center line of piece, BS...Batsug deposit body.

Claims (1)

Claims: 1. A flat tubular web formed of a thermoplastic web is advanced intermittently in uniform increments along a path toward a hermetic cutting station, and the hermetic cutting station hermetically cuts the web. a method of manufacturing a thermoplastic bag to form a web piece of a desired size, comprising: advancing the web a predetermined length into the area of a punching device 76 before sealing the web; the predetermined length; forming at least one pair of holes 130 at symmetrically spaced locations on either side of the longitudinal centerline CP of the web, which has been advanced by a length of CP; A piece of web having a predetermined width is cut in a sealed manner at 66 to obtain a pair of symmetrical bugs on both sides of the center line CP.
Step of forming WS; the same number of pins 9 as the number of holes drilled in the web
depositing the web piece on a deposition device 88 located at a deposition station SS, the web piece passing through the hole in the web, the web piece passing through the pin of the deposition device; When a predetermined number of web pieces are deposited on the device, the deposition device is transferred to the cutting device 1.
02; and cutting the web piece stack midway between the pins along the centerline with the cutting device 102, thereby cutting the web strips held by the pins on the deposition device. A method of manufacturing a thermoplastic bag comprising the step of forming a stack of bags. 2. In the method for manufacturing a thermoplastic bag according to claim 1, the method comprises: vertically spaced apart from the pair of holes, parallel to the center line, and symmetrical to the pair of holes; A method of manufacturing a thermoplastic bag comprising the step of punching another pair of holes 130 in the web by the punching device 76. 3. In the method for manufacturing a thermoplastic bag according to claim 1 or 2, the web piece stack deposited on the depositing device 88 is cut into the pins by the cutting device 102. A method of manufacturing a thermoplastic bag comprising the step of cutting with a heated knife 104 movable in a vertical plane including said centerline CP passing therethrough. 4. In the method for manufacturing a thermoplastic bag according to claim 3, when cutting the web piece stack, the heating knife is rotated at an angle of 93 degrees to prevent adjoining web pieces in the web piece stack from welding. A method of manufacturing a thermoplastic bag comprising the step of heating the web piece stack to 105°C and cutting the web piece stack. 5. In the method for manufacturing a thermoplastic bag according to claim 3, when the web piece stack is cut, adjacent web pieces in the web piece stack are welded and mutually connected blocks of the bag are formed. A method of making a thermoplastic bag comprising the step of heating said heating knife to about 298°C to obtain a thermoplastic bag. 6. A method of manufacturing a thermoplastic bag according to any one of claims 1 to 5, wherein the web piece having holes punched by the punching device 76 is removed from the sealed cutting station 66. transporting the perforated web piece along an arcuate path at about 180° C. to the deposition station SS; and passing the perforated web piece through the upright pin from the deposition device located in the deposition station SS. A method for producing a thermoplastic bag containing. 7. An apparatus for manufacturing thermoplastic bags, comprising: a sealed cutting station 66 for forming a continuous web piece so that two bags are obtained from a flattened tubular thermoplastic web piece; provided downstream of said sealed cutting station; a rotary transfer device 86; and a deposition device 88 having a pin 90, the rotary transfer device depositing the web pieces from the sealed cutting station in a stack onto pins of a deposition device 88 suspended from the conveyor. The bag manufacturing apparatus is further provided with a cutting device 102, which cuts the web pieces at a point where the pile of web pieces is conveyed downstream from the deposition point by the conveyor. Apparatus for producing thermoplastic bags, wherein two bags can be formed from each web piece by cutting the stack. 8. The thermoplastic bag manufacturing apparatus according to claim 7, wherein the pin is aligned with the longitudinal centerline CP of the depositing device.
are arranged in alignment at a distance from each other on opposite sides of the web so that the web pieces are deposited through the pins onto the deposition device, and the cutting device 102 is configured to The stator 14 can be raised and lowered.
8. It has an actuating rod 140 to which the knife 104 is attached in cooperation with the spacer 150, the holder 152, and the clamp bar 154, and a liftable pressing plate 160 is attached to the spring 16 on both sides of the center line CP.
4, the pressing plate pressing against the side edge of the bag to be manufactured before cutting the web stack. 9. An apparatus for manufacturing thermoplastic bags from a roll of flattened and tubular web material formed from a thermoplastic web, comprising: a web advancing device 64 for intermittently advancing said web in uniform increments; during periods of rest of said web; a punch device 76 for punching at least one hole on each side of the longitudinal centerline of the web before sealingly cutting the web; extending transversely with respect to the advancement path of the web for sealing a leading portion of the web; , a sealed cutting device provided in the sealed cutting station 66 for cutting to obtain web pieces WS; and a rotation for conveying each said web piece once it has been formed onto a deposition device 88 in a deposition station SS. a transfer device 86; the depositing device 88 has pins 90 through which each web piece is threaded with pins equal to the number of holes drilled in the web pieces; and the depositing device is indexable. intermittently brought to the deposition station by a conveyor 92 so that, during stops of the conveyor, the web pieces are stacked as a stack on the deposition device through the pins, the conveyor being located at the deposition station; Once a predetermined quantity of the web pieces has been deposited on the deposition device, the bag making device is again advanced to bring a subsequent deposition device to the deposition station, and the bag making device further comprises: A thermoplastic bag having a cutting device 102 spaced apart downstream of the passageway for cutting said pile of web pieces along its longitudinal centerline, thereby obtaining two groups of bag piles at one time. manufacturing equipment. 10 In the thermoplastic bag manufacturing apparatus according to claim 9, the punch device 76 includes two
two reciprocatable pneumatic actuators 125 each having four punches, said pneumatic actuators spaced longitudinally with respect to the path of said web for punching four holes in said web piece; Thermoplastic bag manufacturing equipment. 11. The thermoplastic bag manufacturing apparatus of claim 9, wherein the depositing device 88 includes a generally rectangular plate 172 supporting a central portion of the web piece, and a flexible plate 172 protecting the cutting device 102. Thermoplastic bag manufacturing apparatus having block 174. 12. In the thermoplastic bag manufacturing apparatus according to claim 9, the cutting device 102 comprises:
a holder 152 reciprocatable up and down for holding a serrated knife 104, an electric temperature controller for heating the knife and the holder to a desired temperature, and a holder 152 disposed in a coplanar manner on either side of the knife to control the web piece. A thermoplastic bag manufacturing apparatus comprising a pressing plate 160 for pressing the stack before and during cutting of the stack. 13. The thermoplastic bag manufacturing apparatus according to claim 9, wherein the rotary transfer device 86 has a pair of arms 84 located on both sides of the hole in the web piece. 14. In an apparatus for manufacturing thermoplastic bags, a web advancement device for intermittently advancing a flat, tubular web made of thermoplastic material; a punching device 76 for punching holes; a sealing cutting device provided at a sealing cutting station 66 for cutting the web transversely with respect to the direction of advancement of the web and sealing the web to form the perforated web pieces; a deposition device 88 having pins 90 rising from a rigid plate 172 and spaced apart from each other to correspond to the hole-to-hole spacing on either side of the centerline of the web piece; A rotary transfer device that arranges each of the web pieces along an arcuate path on a deposition device in which each of the web pieces is passed through the pin so that a central portion of the web piece is located on the plate to form a deposit. 86; a conveyor 92 for transporting the deposition device downstream from the deposition station SS to a remote location once a predetermined number of web pieces have been deposited on the plate;
and a cutting device 102 located downstream from the deposition station, the device cutting the stack of web pieces along the centerline or cutting and welding the stack on the deposition device. An apparatus for producing thermoplastic bags, in which two groups of bags are obtained from said pile of web pieces held by pins.